Electrical energy storage devices, such as capacitors, batteries, and ultracapacitors, store or create energy by utilizing the electric charge on two metal or otherwise electrically conductive surfaces (“electrodes”). The charge-bearing surfaces are typically separated by an electrical insulator, or dielectric. As charge is placed on the conductive surfaces, an electrical field is established between the electrodes, resulting in a voltage. Typically, a capacitor physically separates positive and negative charges, rather than chemically separating the charges, as is common in batteries. Batteries have limited ability to be recycled and cannot deliver energy as quickly as a capacitor, or without greater losses than occurs with capacitors.
A supercapacitor or ultracapacitor is sometimes called a double-layer capacitor, as it polarizes an electrolytic solution to store energy electrostatically. The energy storage mechanism of an ultracapacitor is highly reversible, which allows for the ultracapacitor to be charged and discharged many times.
Since one property of an ultracapacitor's capacitance, or energy storage ability, depends on the surface area of the electrodes, some ultracapacitors in use today utilize loose carbon powder or other sintered metal powder to try to increase the surface area of the electrodes. However, the carbon powder tends to accumulate at specific points on the electrodes, rather than stay more evenly dispersed throughout the surface area of the electrode. Furthermore, there is an intrinsic limit to the porosity of these materials, and a limit to the amount of surface area that can be attained simply by making smaller and smaller particles. Thus, there exists a need for increasing the capacitance of capacitors, particularly supercapacitors or ultracapacitors. The present invention fulfills this need, and others.